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Re: LF: alternative antenna for 136kHz

To: [email protected]
Subject: Re: LF: alternative antenna for 136kHz
From: [email protected]
Date: Thu, 24 Oct 2002 17:04:18 EDT
Reply-to: [email protected]
Sender: <[email protected]>
Hi Rik,

Looks to me as if the net result is simply going to be a small loop in series with a series-resonant circuit.

If antenna dimensions are an appreciable fraction of a wavelength, lumped reactances will start to affect the current distribution within a loop (or its variant, the line antenna) and thus affect its radiating properties. For an amateur-size loop, however, the current will be of the same magnitude and direction all the way around, even with the reactances present.

In this design, it is true that there will be high voltages across the reactive components. But since it is accelerated units of charge which emit electromagnetic waves, merely having high electric fields present that contribute nothing to current in the antenna means only that there is increased risk of loss due to surrounding objects. And, it will be necessary to closely watch the Q of the coil, just as with a short vertical antenna. In a sense, such an antenna may represent the worst of both worlds (loop and monopole).

Still, I don't mean to discourage anyone from trying. I think it speaks admirably for the human spirit that LowFERs strive to radiate useful signals from modest gardens, in the face of continual resistance from landlords, neighborhood associations, planning boards, and still higher forms of authority such as spouses.

It can't be easy.

73,
John


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